Disconnect coupling

Abstract

A torque-dependent releasable disconnect coupling for an electric hand-held power tool, in particular a screwdriver, for selectively transmitting a torque from a drive shaft to an output shaft that is coaxial with respect to the drive shaft. An axially nondisplaceable guide ring guides a switching element, in particular a ball, and a second guide ring. A cam ring and the second guide ring are axially pretensioned against one another and accommodate the switching element axially between them. The disconnect coupling may be brought from a first, non-torque-transmitting switching position into a second, torque-transmitting switching position. The switching element is deflected in the axial direction relative to the cam ring, against the action of the pretensioning, when a first release torque in the first switching position is exceeded, thus bringing he disconnect coupling into the second switching position.

What is claimed is: 
     
         1 . A torque-dependent releasable disconnect coupling for an electric hand-held power tool to selectively transmit a torque from a drive shaft to an output shaft that is coaxial with respect to the drive shaft, the disconnect coupling comprising:
 a cam ring that is rotatably fixedly connectable to the drive shaft or to the output shaft;   an axially nondisplaceable first guide ring that is rotatably fixedly connectable to the other of the drive shaft and the output shaft;   at least one switching element or a ball, that is guided from the first guide ring in a circumferential direction and/or in a radial direction; and   a second guide ring, the cam ring and the second guide ring being axially pretensioned against one another and accommodate the at least one switching element arranged axially between them,   wherein the disconnect coupling is adapted to be brought from a first switching position, in which the cam ring is connected in a torque-transmitting manner to the first guide ring in a first rotational direction or clockwise in the axial direction viewed from the drive shaft toward the output shaft, into a second switching position in which the cam ring is freely rotatable with respect to the first guide ring, and   wherein the cam ring is designed such that when the disconnect coupling is in the first switching position, the at least one switching element is deflected in the axial direction relative to the cam ring against the action of the pretensioning when a first release torque that acts in the first rotational direction is exceeded, as a result of which the disconnect coupling is brought into the second switching position.   
     
     
         2 . The disconnect coupling according to  claim 1 , wherein the cam ring comprises:
 at least one depression or a ball pocket, in which the at least one switching element is accommodated in the first switching position, wherein the at least one depression forms a first switching cam against which the at least one switching element rests in the first switching position;   a freewheeling track closed in the circumferential direction, and on which the at least one switching element circulates in the second switching position; and   at least one discharge track that connects the at least one depression and the freewheeling track, and on which the at least one switching element is adapted to move from the at least one depression to the freewheeling track and vice versa,   wherein, when the first release torque is exceeded, the at least one switching element is deflectable in the axial direction, and the disconnect coupling is brought into the second switching position by moving the at least one switching element from the at least one depression, via the at least one discharge track, into the freewheeling track.   
     
     
         3 . The disconnect coupling according to  claim 2 , wherein the axial level of the at least one discharge track rises from the depression in the direction of the freewheeling track, and is always lower than or at the same height as the axial level of the freewheeling track. 
     
     
         4 . The disconnect coupling according to  claim 1 , wherein the first guide ring is designed as a cage ring having at least one through opening, and the at least one switching element is accommodated in the at least one through opening. 
     
     
         5 . The disconnect coupling according to  claim 4 , wherein the at least one through opening has an elongated shape or an elongated straight shape, whose direction of extension is inclined with respect to a radial direction. 
     
     
         6 . The disconnect coupling according to  claim 2 , wherein the at least one depression inside the cam ring is spaced apart from the outer circumference of the cam ring. 
     
     
         7 . The disconnect coupling according to  claim 2 , wherein the freewheeling track has a constant axial level. 
     
     
         8 . The disconnect coupling according to  claim 2 , wherein the at least one discharge track has, at least in part, the shape of a logarithmic spiral. 
     
     
         9 . The disconnect coupling according to  claim 1 , wherein the disconnect coupling is adapted to be brought from a third switching position, in which the cam ring is connected in a torque-transmitting manner to the first guide ring in a second rotational direction opposite to the first rotational direction or counterclockwise in the axial direction viewed from the drive shaft toward the output shaft, into a fourth switching position in which the cam ring is freely rotatable with respect to the first guide ring, and
 wherein the cam ring is designed in such a way that when the disconnect coupling is in the third switching position, the at least one switching element is deflected in the axial direction relative to the cam ring against the effect of the pretensioning, when a second release torque that acts in the second rotational direction is exceeded, as a result of which the disconnect coupling is brought into the fourth switching position.   
     
     
         10 . The disconnect coupling according to  claim 2 , wherein the at least one switching element in the third switching position is accommodated in the at least one depression, wherein the at least one depression forms a second switching cam against which the at least one switching element rests in the third switching position, wherein the cam ring also has a cam track that is largely closed in the circumferential direction and interrupted only by the at least one depression, and on which the at least one switching element in the fourth switching position can circulate, at least in parts, wherein the at least one switching element is deflectable in the axial direction when the second release torque is exceeded, and the disconnect coupling may be brought into the fourth switching position by moving the at least one switching element from the at least one depression into the cam track. 
     
     
         11 . The disconnect coupling according to  claim 1 , wherein the disconnect coupling has a freewheel that is adapted to be opened and closed, and which is configured to be supported on a housing of the electric hand-held power tool, and which in the closed state allows rotation of the output shaft in the first rotational direction and blocks rotation of the output shaft in the second rotational direction, and in the open state does not affect the rotatability of the output shaft. 
     
     
         12 . The disconnect coupling according to  claim 11 , wherein the freewheel is a ratchet-type freewheel in which at least one freewheel ratchet engages with at least one freewheel tooth, wherein the at least one freewheel ratchet is situated on an axially displaceable, nonrotatable freewheel ratchet ring that is axially pretensioned against the at least one freewheel tooth, and the at least one freewheel tooth is situated at an end-face side of the first guide ring. 
     
     
         13 . The disconnect coupling according to  claim 12 , wherein the freewheel is adapted to be closed and opened by an axial displacement of the freewheel ratchet ring, which is achieved by axially displacing the second guide ring. 
     
     
         14 . The disconnect coupling according to  claim 12 , wherein the cam ring and the first guide ring are situated axially between the freewheel ratchet ring and the second guide ring, and the second guide ring or a component that is connected to the second guide ring and axially nondisplaceable with respect to same axially overlaps the cam ring and the first guide ring. 
     
     
         15 . An electric hand-held power tool, in particular a screwdriver, comprising a disconnect coupling according to  claim 1 . 
     
     
         16 . The disconnect coupling according to  claim 1 , wherein the power tool is a screwdriver.